Band stop filter for electromagnetic waves



y 1951 H. GUTTON ET AL 2,553,313

BAND STOP FILTER FOR ELECTROMAGNETIC wmzs Filed Dec. 29, 1945 H -+1INVENTOR HENRI GUTTON JEAN ORTUS/ BYW AGENTS Patented May 15, 1951 BANDSTOP FILTER FOR ELECTRO- MAGNETIC WAVES Henri Gutton and Jean Ortusi,Paris, France, as-

signors to Compagnie Generale de Telegraphic Sans Fil, a, corporation ofFrance Application December 29, 1945, Serial N 0. 638,371

In France December 14, 1943 Section 1, Public Law 690, August 8, 1946Patent expires December 14, 1963 8 Claims. (Cl. 17s 44) This inventionrelates to band stop filters for electromagnetic waves propagated in theinterior of a dielectric conductor and has for its object the provisionof an apparatus which, arranged in a conductor of any shape traversed bya suitable wave, permits the transmission of electromagnetic waves overa definite width of band embracing a fixed frequency to be stopped,whilst fully ensuring the transmission of the other frequencies. Thewidth of band passing through the filter determines the selectivity ofthe filter.

The invention consists essentially in arranging in the interior of theconductor a conductor frame the section and the angular setting ororientation of which may be modified as desired from the exterior, meansfor adjusting the section and the orientation being, furthermore,provided.

The invention will be readily understood by reference to theaccompanying drawings which give by way of example one method ofcarrying the invention into effect. The example of the application ofthe invention described relates to the case of conductors of rectangularsection traversed by a wave of the H01 type, but it will be appreciatedby any one skilled in the art that the invention may be adapted to othertypes of conductors and waves.

In the drawings:

Figure 1 illustrates in elevation and in section an apparatusconstructed in accordance with the present invention;

Figure 2 is a plan view of Figure 1; and

Figures 3a and 3b are are transmission curves of a conductor providedwith an apparatus constructed in accordance with the invention; thecurve in Figure 3a is drawn corresponding to the angle of orientation ofthe frame and the curve in Figure 3b is drawn corresponding to thelength of the frame.

Referring to the drawings, a conductor frame of rectangular profile ABCDis arranged in the interior of the conductor G (Figures 1 and 2). Thelongitudinal axis of the frame is coaxial with longitudinal symmetricalaxis ZOZ' of the upright section of the conductor. The frame is carriedby rods E and F arranged coaxially with the said axis ZOZ'. The upperrod E is provided with a disc N, of a thickness corresponding to that ofthe wall, and confined, with a certain lateral play, between two otherbored discs M and M between which it can rotate and slide slightly. Thelower rod F is provided with a terminal swivel joint U fitted in aspherical recess carried by the extremity of a threaded rod Lconstituting an extension of the rod F, and screwing into and throughthe wall of the conductor G where it terminates outside in a knob B1.The length of the frame may be made variable by telescoping the lowerpart of the frame (whichmay be made of a hollow tube) over the upperfixed part. This sliding action is effected without any change in theorientation of the plane of the frame by means of the threaded screwactuated through the medium of the knob B1. A spring K, arranged in theinterior of the sliding tube, connects the lower and upper parts of theframe, and permits of a displacement corresponding to the threadedlength of the screw L.

The whole of the frame as far as the spherical head U is rotatable aboutthe axis thereof by means of the two toothed wheels 01 and C2. The wheelC2 is rotatable about an axis 0' through the medium of a rod L connectedto a knob B2 and is operable to rotate the wheel C1 which is connectedto the rod E. The angle of rotation of the knob 31 which can be read ona scale, denotes the length Z of the frame. The angle of rotation of theknob B2, also indicated on a dial,

enables the angle 6 from the normal of the plane of the frame with thepropagation axis of the conductor to be determined.

The indications read on the scales of the said length and angle,together with the curves of variation of the coefiicient of transmissioncorresponding with the angle of the frame or its length, are employed todetermine according to the values chosen, the corresponding coefficientand the band width or, conversely, to determine the angle and the lengthaccording to the coefiicient of transmission and the width of banddesired.

The value of the coeflicient of transmission of a wave H01 of frequencyN and wavelength may be determined as a function of l and of 0 and theremay be traced either the curves T=f1(0) with Z as parameter, or thecurves T=f2 (Z) with 0 as parameter.

There are obtained the two groups of curves of the Figures 3a and 3b. InFigure 3a, 01, stands for the angle orientation of the frame whenl=Z1+dZ1 and T= /2. And in Figure 31), lo stands for the minimumdistance AD when the upper part of the frame extends as far as possibleinto the hollow tubes of the lower part of the frame and the springs aremost compressed.

Assuming that the frame is tuned at Z1 in resonance on the frequency Nof wave x, if I is maintained at Z1 curve T=f1 (0) will be that.

marked Z1 on Figure 3a passing through points assaaie ABCDI. On Figure3b the corresponding points will be abcdi all located on the line 1:11.

If, however, the length of the frame varies. by an amount dli the frameis no longer; tuned to frequency N and even for a value =1r/2 the wavewill no longer be completely arrested and curve.

T=f1 (0) will pass through points ABCD'I' on Figure 3a marked Z1+dl1.

On Figure 3b't-he cor responding points will be a'b'cdi' all onthe in adirection perpendicular toyrthe wafls of the guide, a threaded stemprolonging the axis of 1 said other member through a wall of the guideThe same procedure can. beapplied to each value of Z giving the curvesof Figure 3a. Further'-- more, since points ABCD, A'BM'C'D' etc.correspond to specific valves of 0 (respectively 7r/2,'1r/4,.

1r/5, 1r/l4) by joining on Figure 3b such points as ea, bb, cc, dd etc.the group of. curves ob;-

tained on this figure will also correspond to those valves of 0. Thedotted lines connectingthe two figures clearly show how the curvescorrespond.

Moreover on Figure 3b, the curve for 0:0 will of course correspond toT=1 since the frame'oifers no resistance to the wave in this position.

What we claim is:

1. In a. guide-for ultra-short electro-magnetic waves, a frame havingthe same cross-sectional shape as the guide taken in a planeperpendicular' to the walls thereof, said frame being tuned to admit thefrequency of a given wave among those carried by the guide, and meansfor varying the angular setting of said frame about an axis contained inthe plane thereof and perpendicular tothe wall of the guide.

2. In a guide as claimed in claim 1, means for varying the size of saidframe while preserving the shape thereof.

' 3. In a' rectangular guide for ultra-short electromagnetic Waves, arectangular frame tuned to admit the frequency of a given wave amongthose carried by the guide, and means for varying, the angular settingof said frame about an axis contained in the plane thereof, parallel totwo of the sides thereof andperpendicular tothe walls of the guide.

4. In arectangular guide as claimed in claim 3, means for varying thelength of the sides of said frame parallel to said axis.

5. In a rectangular guide excited with waves of the H01 type, arectangular frame comprising two substantially U-shaped members, one ofsaid members having hollow arms adapted to accommodate telescopicallythe arms of the other of said members, one of said members being heldagainst translational movement but rotatable about its own axis andhaving a stem rigid therewith and prolonging said axis through a wall ofthe guide, an adjustment knob outside the guide opposite saidfirst-mentioned stem, a rotary joint connecting said threaded stem tosaid other member, internally threaded means connected to the wall. ofthe guide and threadedly engaging saidthreaded stem,an adjustment knobon the outer. extremity of said threaded stem rotation of which willeffect said translational movement and a ust the telescopic relationshipof said members, and return springs in said hollow arms yieldablyurging.said members apart in all adjustedxpositions to prevent back-lash.

6. The guide as claimed in claim 1, wherein the saidframe is free ofcontact with the walls of the guide except at the location therein ofthe means for varying the angular setting.

7 Aband stop filter for a guide of ultra short.

electromagnetic wavespropagated thereby, com-..

prising a conductor frame of adjustable section and orientation arrangedin the interior of the quency, according to the width of the frequency"band to be stopped. 8'. A band stopfilteras claimed in claim 7, arrangedfor a rectangular guide excited in Hot waves comprising a. rectangularframe, one of the symmetrical axes of which is arranged ma normal"section of the guide and according to the axis of this section normal tothe electric vector, means mounting the said frame for rotation aboutthe said axis, the two sides of said framewhich are parallel to the saidaxis being extensible';

HENRI GUTTON. JEAN ORTUSI.

" REFERENCES CITED The following references are of record in the fileofthis patent:

UNITED STATES PATENTS Number Name Date 2,197,123 King Apr. 1 6, 1940"2,432,093. Fox Dec. 9, 1947

